Not applicable.
Not applicable.
Not applicable.
(1) Field of the Invention
The invention relates to the field of building up land in water-covered or water-surrounded areas and more specifically to the field of restoring land in coastal wetlands where erosion has caused land loss.
(2) Description of the Related Art
Coastal wetlands historically have been rich in plant and animal life. This abundance of plant and animal life has made coastal wetlands productive areas for fishing (for fish and shellfish), trapping, and hunting.
Coastal wetlands require a constant supply of sediment so that the process of sedimentation keeps pace with erosion. In a coastal wetland, the land is built up by sedimentation and broken down by erosion. In a stable coastal wetland, these processes are in balance when considered over the long term: land loss through erosion and land gain from sedimentation remain essentially equal. Seasonal or unusual events such as floods or storms may cause erosion and sedimentation to become unbalanced for a time. But in a stable wetland, erosion and sedimentation remain in balance over the long term.
Over at least the last 100 years, human activities have affected the natural balance between erosion and sedimentation in many coastal wetlands. Levees and other developments have reduced the flow of fresh water into many coastal wetlands. These developments have reduced the amount of sedimentation in the affected coastal wetlands by eliminating the sediment flows that were carried by the fresh water flow.
In addition to reducing sedimentation, the reduction of fresh water flow has also promoted erosion. The reduction of fresh water flow has changed the chemical compositionxe2x80x94especially the salinityxe2x80x94of water in some coastal wetlands. Plants adapted to the previous (lower) salinity levels often die when salinity increases. Killing the plants increases erosion because many plants hold the land together and help to absorb impacts of waves and other water flows. When the plants die, erosion increases.
With erosion increasing and sedimentation decreasing, land area in coastal wetlands has shrunk. Facing the loss of a valuable resource, public officials and citizens have sought ways to reduce erosion and increase sedimentation in coastal wetlands so that lost land may be restored. Fresh water diversion from rivers into coastal wetlands merely keeps salt water at bay and does little to promote land restoration, not only because of decreased sediment in leveed rivers but also because diversion of fresh water typically uses siphons or pipes that place sediment-containing water into a single location rather than over a broader plain. Rivers currently contain seventy percent less sediment than they did fifty years ago because of flood-prevention methods upstream.
Various devices for building up land in a water-covered area have been disclosed to aid in reducing and reversing land loss. U.S. Pat. No. 6,190,088 to Van Der Hidde et al. discloses a device for forming a sand body. The device comprises a substantially rectangular portion of water-permeable cloth. The cloth is held to the water bottom on three of its four sides by anchors and sediment pouches. The fourth side of the cloth is held above the water bottom by floating elements. The cloth thus forms a water-permeable pouch. Sediment-containing water flow enters the open end of the pouch and is trapped, eventually forming a sand body. Van Der Hidde""s device appears to be intended to promote sedimentation by entrapping sediment that is being moved about by natural currents. The device does not appear to be suited for use in areas where no natural sediment-containing flow is available, such as a coastal wetland where former sediment-containing water flows have been reduced or eliminated by levees.
In contrast to Van Der Hidde""s cloth pouch, other patents disclose rigid, non-floating barriers intended for use in building up land. U.S. Pat. No. 3,835,651 to Butterworth et al. discloses a rigid, piling-supported barrier for use in building up land. Butterworth""s device comprises a system of rigid bulkheads that slow a sediment-charged flow, causing deposition of sediment and the eventual formation of land. Butterworth""s device also includes additional bulkheads that prevent erosion by reducing the impact force of waves striking the shore. Butterworth""s device appears to be specially adapted for use where wave action is present, such as the shores of lakes and oceans.
Another rigid, piling-supported device is disclosed by U.S. Pat. No. 4,089,179 to Trautman. Trautman discloses a device comprising a rigid, post-supported frame with screened louvers mounted thereon. The device allows waves, which carry sediment, to pass freely toward shore; but it slows flow away from shore, causing sediment to be deposited near the shore. Thus the device causes a sand body to be formed.
U.S. Pat. No. 5,007,766 to Freed et al. discloses a sediment barrier for reducing erosion that occurs when water flows across land. The barrier comprises an array of fibers emanating upward from a foundation; the fibers reduce erosion by reducing the velocity of water that flows through the device.
Several patents disclose floating barriers, but these patents do not disclose the use of the barriers to control erosion or to build up land. For example, U.S. Pat. No. 3,984,987 to Light discloses an apparatus for preventing silt from entering a marine facility and for confining spills of pollutants within the facility. Light""s device comprises a floating barrier secured across the opening of the facility and a flexible curtain having means for anchoring the curtain to the floor of the water body. Light discloses that the device may be used to avoid silt buildup in a facility, but Light does not disclose any use of the device to control erosion or to build up land.
Another floating barrier is disclosed by U.S. Pat. No. 4,190,381 to Kraus et al. Kraus discloses that the device may be used for collecting material floating upon the surface of a body of water. The device comprises a plurality of floating elements that are connected to a barrier. The barrier has an upper or freeboard position and a lower or skirt portion extending downward into a body of water. Attached to the barrier""s skirt and extending downward therefrom is a lattice containing a plurality of strands made from an extensible material. The lower portion of the lattice is connected to a bottom tension line, which is shorter in length than the corresponding portion of the barrier. Kraus""s device is adapted to confine a liquid spill that floats upon a body of water. The device is not adapted for building up land.
U.S. Pat. No. 4,688,024 to Gadde discloses a barrier comprising a floating lift hose, an anchoring body, and a net extending therebetween. Gadde discloses that the device is useful for blocking a water passage or channel against the admission of a foreign or unfamiliar object, such as an underwater vessel, frogman, or the like.
Finally, U.S. Pat. No. 5,927,899 to Claesson discloses an arrangement for a floating body comprising containers made from a flexible material positioned laterally in relation to one another and capable of being filled with air or other gas. The prior art does not disclose or suggest that the floating bodies described therein can be used to confine sediment to build up land in a water-covered or water-surrounded area.
It is an object of this invention to provide a method and system for building up land in a water-covered area. It is another object of this invention to provide a floating structure capable of confining sediment. To achieve these and other advantages and objects, and in accordance with the purpose of the invention as embodied and broadly described herein, in one aspect the inventor describes a method for building up land in a water-covered area.
In a first embodiment, the method includes the steps of: supplying a floating structure having an essentially closed shape and capable of confining sediment; selecting a location in which land is to be built up; placing the floating structure at the location; and introducing a sediment-containing water flow into the interior of the essentially closed shape.
Further in accordance with the purpose of the invention as embodied and broadly described herein, in another aspect, the inventor describes in a system for building up land in a water-covered area. The system includes a plurality of floating boom segments, a wasteweir segment, and a sediment source. The boom segments and the wasteweir segment are connectable to form a shape that encloses an area wherein land is to be built up. The boom segments are connectable by connecting means as described further below. Each boom segment has a body that has a sieve panel attached thereto. Thus the assembled device includes an essentially closed shape formed by the boom segments and interrupted by the wasteweir segment. The assembled device also includes an essentially closed shape extending essentially between the water surface and the water bottom and interrupted by the wasteweir segment. The wasteweir segment enhances the rate of land formation by increasing the rate at which water pumped in by the sediment source may leave the enclosed area. Other embodiments of the invention may include multiple wasteweir segments or may omit wasteweir segments entirely.
In the first embodiment of a system for building up land in a water-covered area, each boom segment has a floatable body having a first end portion, a second end portion, and a lower side portion; a first means for connecting the body attached to the first end portion and a second means for connecting the body attached to the second end portion; and a sieve panel attached to the lower side portion. The floating body is formed from buoyant material and may be formed in any convenient fashion allowing attachment of the sieve panel and the means for connecting the body. In the first embodiment, the floatable body is preferably made from a buoyant foam material. The foam material is preferably sealed within a skin of vinyl cloth. The skin is preferably equipped with grommeted holes for attaching means for connecting the body.
In the first embodiment, the sieve panel of each boom segment is preferably heat-bonded to the vinyl skin of the floatable body. The sieve panel of each boom segment has a generally rectangular shape and an upper portion, a lower portion, and first and second side portions, the first and second side portions of the sieve panel being respectively aligned with the first and second end portions of the body. Each first side portion of the sieve panel has disposed thereon a first means for connecting sieve panel; likewise, each second side portion of the sieve panel has disposed thereon second means for attaching sieve panel. In the first embodiment the means for connecting sieve panels are two connectible portions of a zipper. Other means, including ropes, cords, snaps, interlocking rigid connectors, and heat bonding, may also be used as sieve-panel connecting means. Each sieve panel has a height greater than or approximately equal to the depth of the water in the water-covered area and preferably has a height approximately twice the depth of the water in the water-covered area in order to create a terracing effect around the perimeter and to thereby mimic a naturally-sloped shoreline. Here the height of a sieve panel is the distance between its upper portion and its lower portion, measured with the sieve panel laid out upon a flat surface. When the sieve panel has a height greater than the depth of the water in which the sieve panel is used, the fact that the height of the sieve panel itself is greater that the water depth allows the sieve to bulge outward in a curved shape; for example, see FIG. 7.
In a preferred embodiment, the mesh of the sieve panel is approximately {fraction (1/16)} inch. This allows for vegetation to take root and be anchored to the sieve panel.
Optionally, each sieve panel has an anchor segment attached to and preferably running the length of its lower portion, the anchor segment being a segment of lead-core line, chain, or other similar dense, non-floating, generally linear material. The anchor segment helps to hold the lower portion of the sieve panel to the bottom of the water-covered area. Each boom segment has an anchor segment having a first end portion aligned with the first end portion of the floatable body and a second end portion aligned with the second end portion of the floatable body. Each anchor segment has first anchor connecting means disposed upon the first end portion thereof and second anchor connecting means disposed upon the second end portion thereof.
Optionally, each boom segment can also include a tiedown having a first end portion and a second end portion, the first end portion being attached to the body. The tiedown is secured so that its length under tension is approximately equal to the depth of the water and the length of the tiedown is at least approximately equal to the depth of the water. Preferably, the tiedown is fastened to the anchor line such that its length approximately equals the depth of the water. Tiedowns are intended to add strength to the boom segments and to keep the boom segments at the height of the wasteweir.
In the first embodiment the wasteweir segment is an essentially U-shaped frame having a height at least approximately equal to the depth of the water in the water-covered area. The frame is constructed so that it is denser than water. Aluminum, steel, or other appropriate materials can be used for the frame material. The wasteweir segment includes a first wasteweir-to-body connecting means allowing it to be connected to the second body-connecting means and a second wasteweir-to-body connecting means allowing it to be connected to the first body-connecting means. The wasteweir segment also includes means for connecting it to the first and second sieve-panel attaching means. The wasteweir segment also includes wasteweir-to-anchor connecting means disposed thereon to allow for connection to the anchor segments of boom segments adjacent to the wasteweir segment. By use of its various connecting means, the wasteweir segment may be inserted and connected as part of an assembly of boom segments. The wasteweir segment also includes barriers, which in the first embodiment are preferably ordinary wooden boards. The barriers are connectible to the wasteweir frame via barrier receiving means, which are grooves in the wasteweir frame as in the second embodiment.
The first embodiment also has a sediment source disposed so as to provide sediment flow into the interior of the closed shape formed by the boom segments and the wasteweir segment. The sediment source in the first embodiment is preferably the discharge of a dredge.
In an alternative embodiment, the sieve panel of each boom segment does not have an anchor line attached thereto. Instead, a single anchor line of the desired length is attached to the sieve panels, to the tiedowns of each segment, and to the wasteweir segment, thus running the length of the device.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and do not restrict the invention as claimed.